Field of the Invention
The invention relates to a cylinder-and-piston assembly for a bottle attachment apparatus for handling liquids, and to a bottle attachment apparatus for handling liquids.
Description of Related Art
In the case of bottle attachment apparatuses for handling liquids, the focus is on precisely measuring and conveying liquids from a storage bottle or another storage container, wherein precise measuring is performed when a partial volume of liquid is received from the storage bottle or similar into the apparatus and/or when a partial volume of liquid is externally dispensed from the apparatus into a container.
Bottle attachment apparatus of the type being discussed are in particular bottle attachment dispensers and burettes. Bottle attachment apparatuses of this type are widely used in chemical, biological, and pharmaceutical laboratories and production facilities.
The term “liquid” in the present context preferably refers to liquids as are used in chemical, biological, and pharmaceutical laboratories and production facilities etc. These are preferably liquids having a relative viscosity of up to about 300 (viscosity relative to the viscosity of water, measured at normal conditions). In colloquial terms, the liquids are thus preferably those in the range of very low viscosity to slightly viscous.
In the case of bottle attachment apparatuses of the type being discussed, high requirements are set for volume accuracy of liquid intake and/or liquid dispensation, and for operator safety. The bottle attachment apparatuses are usually operated manually or else are driven by an actuator.
A typical example of a bottle attachment apparatus in the form of a bottle top dispenser is known from European Patent Application EP 0 542 241 A2. The present invention proceeds from this prior art. For bottle attachment apparatuses in the form of bottle top dispensers, reference is made to the entire content of European Patent Application EP 0 542 241 A2.
In an exemplary manner, a bottle attachment apparatus in the form of a buret is known from European Patent Application EP 2 799 141 A2 and corresponding U.S. Pat. No. 8,142,738 B2. A bottle attachment apparatus in the form of burette has many construction details in common with a bottle attachment apparatus in the form of a bottle top dispenser. Also to this extent, reference is made to the entire content of European Patent Application EP 2 799 141 A2 and corresponding U.S. Pat. No. 8,142,738 B2.
Here and hereunder, a bottle attachment apparatus is always described in the operating position thereof, that is to say in the position thereof when fastened to a storage bottle or similar, and when aligned in a substantially vertical manner. A valve block assembly for such a bottle attachment apparatus is also described in a corresponding manner, that is to say likewise in the operating position thereof, that is to say when installed in a bottle attachment apparatus in the operating position thereof.
A substantial component part of a bottle attachment apparatus of the type being discussed is the cylinder-and-piston assembly with the aid of which the liquid may be suctioned and exhausted again. Said cylinder-and-piston assembly has a cylinder which defines a longitudinal direction, and a piston which is guided in a sealed manner in the cylinder so as to be longitudinally displaceable. In the event of an upward movement of the piston in the cylinder, the liquid is suctioned by forming negative pressure in the cylinder. In the event of a downward movement, the liquid in the cylinder is exhausted again from the cylinder. The flow of the liquid during suctioning, on the one hand, and during exhausting, on the other hand, is directed by valves of the valve block assembly. The cylinder-and-piston assembly is connected in a sealing manner to the valve block assembly and to the lines which are located therein. The valve block assembly as such in turn is attached onto the storage bottle or similar with the aid of a fastening assembly.
An intake valve which allows liquid to be suctioned from the storage bottle by means of an intake pipe is located in the valve block of the valve block assembly. The intake pipe, most often in the form of a plug-fitted tube, extends deeply downward into the storage bottle. An exhaust line extends away from the valve block in an approximately horizontal manner. An exhaust valve sits in the exhaust line or in the valve block, so as to be at the beginning of the exhaust line. In some instances, the exhaust line has an additional switching valve by way of which a return flow line leading back into the storage bottle may be opened or closed. At the opening from which the liquid exits, the exhaust line may have a closure.
Since the exhaust line protrudes from the valve block in an approximately horizontal manner and the previously discussed switching valve also often sits there, this is that side from which an operator works on the bottle attachment apparatus. This side may be referred to as the “front side” of the bottle attachment apparatus. The opposite side is the “rear side” of the bottle attachment apparatus. In the case of an electronic design embodiment of a bottle attachment apparatus, a display having corresponding operating elements is preferably located on the front side of the bottle attachment apparatus.
The fastening assembly for fastening the external housing and/or the valve block assembly of the bottle attachment apparatus onto a storage bottle or similar is often a thread assembly which is similar to a union nut, or is an internal thread which is incorporated into the valve block per se, for screwing onto the external thread on a bottleneck of the storage bottle (see the prior art mentioned at the outset). However, in principle other fastening assemblies, such as bayonet systems or short-stroke collets are likewise employable, as are systems of the type of a taper-ground joint, which are usual in laboratories.
The present focus is on the cylinder-and-piston assembly for a bottle attachment apparatus of the type being discussed, and in particular on the stroke length adjustment on the cylinder housing of the cylinder-and-piston assembly.
In the prior art (European Patent Application EP 0 542 241 A2) from which the invention proceeds the cylinder-and-piston assembly has a cylinder housing which is connected to the piston and externally encompasses the cylinder by way of an internal side which faces the cylinder and of an external side which faces away from the cylinder. By displacing the cylinder housing up or down in relation to the cylinder, the piston is displaced in a corresponding manner in the cylinder. The stroke length of the piston in the cylinder is delimited by a fixed stop which interacts with a stroke length stop on the cylinder housing. On account thereof, it is also prevented that the piston may be upwardly extracted from the cylinder.
The cylinder, by way of the central axis thereof, defines a longitudinal direction. The cylinder housing has a longitudinal slot running in the longitudinal direction. A scale which is assigned to the longitudinal slot is located on the external side of the cylinder housing, in most cases on one side next to the longitudinal slot. The scale allows the volume of liquid in the cylinder, which has in each case been set by the cylinder-and-piston assembly, to be identified.
In order for various volumes to be able to be suctioned and exhausted by way of the cylinder-and-piston assembly, the stroke length stop on the cylinder housing is adjustable in the longitudinal direction. The stroke length stop is interlockable in the respectively set position and then defines the stroke length and thus also the volume which has been made available to the liquid in the cylinder.
In the prior art from which the invention proceeds, the stroke length stop has an indicator element which for indicating a specific value on the scale interacts with the scale, an interlocking mount, and a handle. The interlocking mount has a lateral and short row of teeth. An elongate row of teeth on the cylinder housing at the periphery of the longitudinal slot communicates with the row of teeth on the interlocking mount. The two rows of teeth together form a tooth assembly. If an when the rows of teeth are mutually engaged, the interlocking mount is interlocked in the longitudinal direction with the indicator element on the cylinder housing. The engagement of the tooth assembly is maintained by spring force. By actuating the handle counter to the spring force, the rows of teeth of the tooth assembly may be mutually disengaged. If and when the handle is further held in the release position, the handle together with the interlocking mount and the indicator element may be displaced up and down in the longitudinal slot of the cylinder housing until the desired position has been reached. If and when the handle is let go, the stroke length stop is interlocked in this position by the tooth assembly.
A stroke length stop on a cylinder housing of a cylinder-and-piston assembly for a bottle attachment apparatus of the type being discussed, which has an indicator element, an interlocking mount, and an interlocking cap, and which by way of a friction-engagement assembly is interlockable in the respective position on the internal side of the cylinder housing is known from other prior art (German Patent Application DE 23 43 687 A1).
In the case of all cylinder-and-piston assemblies known from the prior art the stroke length stop is loosened so as to be able to adjust the latter in the longitudinal direction on the cylinder housing. The loosened stroke length stop is then also laterally not aligned as well in the longitudinal slot as is the case with the interlocked stroke length stop. The indicator element is somewhat raised above the external side of the cylinder housing. On account thereof, in some instances a certain parallax effect which impedes the selection of the correct and desired volume with the aid of the indicator element and of the scale results. This is the case in some instances in particular with a stroke length stop with a tooth assembly, because the stroke length stop here has to be loosened to a comparatively large extent, so as to disengage the rows of teeth of the tooth assembly for adjusting the stroke length stop.
If and when a handle or an interlocking cap is excessively loosened, the interlocking mount and/or the indicator element are/is disengaged from the peripheries of the longitudinal slot, and prior to interlocking the stroke length stop on the cylinder housing again, the interlocking mount and/or the indicator element have/has to first be rethreaded into the longitudinal slot. Moreover, an excessively loosened interlocking mount in the interior strikes the cylinder and/or tilts together with the indicator element in the longitudinal slot. Both issues are obstacles to adjusting the stroke length stop in the longitudinal slot.
Overall, the known cylinder-and-piston assembly having the stroke length stop in terms of operation is in need of improvement. The teaching is therefore based on the issue of improving a cylinder-and-piston assembly for a bottle attachment apparatus for handling liquids in terms of handling of the stroke length stop in practical use.